Magic Tree House Merlin Missions

I've reviewed the first part of the Magic Tree House series so now I've read Haunted Castle on Hallows Eve. I think it is a very good part of the Magic Tree House Series. The Merlin Mission books are different from the beginning books because Jack and Annie do a lot of different stuff. Merlin sends them on the missions so that is why it is called "Merlin Missions". Haunted Castle is about medieval times. People were very superstitious about the castle. But I'm not going to spoil it. Try reading it yourself.